Ketocarboxylic acids which have the following general formula: ##STR1## wherein R is an alkyl group and X is 1 or 2 have found wide utility as surfactants, British Patent 1,081,234, and as potential flavorants, British Patent 1,053,600, as well as serving as intermediates in the synthesis of more complex materials, such as steroids, Noland, W.F., Ed., "Organic Synthesis", Collective Volume 6, John Wiley & Sons, Inc. New York, 1988, p. 774, and Blickenstaff, R.T.; Ghosh, A.C.; Wolf, G.C.; "Total Synthesis of Steroids", Academic Press, New York, 1974.
In the past, ketocarboxylic acids have been prepared by a number of methods including the hydrolysis of acetylenic esters, Arcadi, A.; Cacchi, S.; Marinelli, F.; Misiti, D.; The Reaction of Alkyl 4-Hydroxy-2-alkynoates and 4-Hydroxy-2-alkyn-1-ones with Palladium Tributylammonium Formate and with Tributylamine: Preparation of 1,4-Dicarbonyl Compounds, Tetrahedron Letters, Volume 29, No. 12, pp. 1457-60, 1988; the reaction of a Grignard reagent upon furfural, followed by hydrolysis, Ponomarev, A.A.; Sedavkina, V.A.; Gamma-Oxoundecanoic Acid, Metody Poluch. Khim. Reakivov Prep. No. 17, pp. 59-62, 1967; and the reaction of a Grignard reagent upon the silyl derivatives of lactones, followed by hydrolysis, Betancourt de Perez, R. M.; Fuentes, L. M.; Larson, G. L.; Barnes, C. L.; Heeg, M. J.; A Synthesis of 4-Ox Carboxylic Acids, 4-Oxo Aldehydes and 1,4-Diketones from Gamma-Lactones, Journal of Organic Chemistry, Volume 51, No. 11, pp. 2039-43, 1986. More recently a wider range of synthetic techniques for preparing ketocarboxylic acids have been employed. These include methods such as the hydrolysis of an addition product of a nitroalkane on acrolein, Ballini, R.; Pertini, M.; Facile and Inexpensive Synthesis of 4-Oxoalkanoic Acids from Primary Nitroalkanes and Acrolein, Synthesis, pp. 1024-26, 1986, or the reaction of an alkyl lithium reagent on a lactone, followed by oxidation of the keto-alcohol, Fernandez, S.; Hernandez, J. E.; Cisneros, A.; Three Step Synthesis of Racemic Lactonic Pheromones, Rev. Latinoam Quim., Volume 16, No. 1, pp. 22-4, 1985.
A number of known syntheses specifically aimed at preparing the alpha ketocarboxylic acids involve the reactions of alkyl halides with carbon monoxide at elevated temperatures with the use of a special catalyst, U.S. Pat.No. 4,738,802; and the oxidation of a lactic acid or amide, followed by hydrolysis, U.S. Pat. Nos. 4,242,525, and 3,897,467.
More general reactions for the preparation of ketocarboxylic acids involve the use of alkyl aluminum compounds, German Patent 1,288,584, German Patent 51,309, Chemical Abstract 70: 77356y (1969); Grignard reagents with a succinic or glutaric anhydride, Japanese Patent 81/161,348; or the alkaline hydrolysis of dihalo-acids, Japanese Patent 69/08,487, Chemical Abstract 71:90833s (1969). Ozone and chromium trioxide have also been used as oxidants for alpha, beta-unsaturated ketones or the corresponding alcohol acids, Japanese Patent 68/22,575, U.S. Pat. No. 4,612,391, U.S. Pat. No. 4,126,748, U.S. Pat. No. 2,848,480, U.S. Pat. No. 1,715,654, and U.S. Pat. No. 3,719,706.
The majority of these known prior art synthetic methods for ketocarboxylic acids involve multi-step reaction schemes followed by a difficult separation to sufficiently purify the ketocarboxylic acid product. It was the aim of this invention to develop a simple process to prepare 4- and 5-ketocarboxylic acids in an economical, one step procedure which would yield a ketocarboxylic acid devoid of unwanted by-products and require minimal separation techniques.